1. Field of the Invention
The present invention relates generally to the field of magnetic disk drives, and more particularly to a design for an air bearing surface of a read/write head for a magnetic disk drive.
2. Description of the Prior Art
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In FIGS. 1 and 2, a magnetic disk data storage system 10 includes an enclosure 12, a disk drive motor 14, and a magnetic disk, or media, 16 supported for rotation by a drive spindle 17 of motor 14. Also included are an actuator 18 and an arm 20 attached to an actuator spindle 21 of actuator 18. A suspension 22 is coupled at one end to the arm 20 and at another end to a read/write head 24. The suspension 22 and the read/write head 24 are commonly collectively referred to as a head gimbal assembly (HGA). The read/write head 24 typically includes an inductive write element and a magnetoresistive read element that are held in a very close proximity to the magnetic disk 16. As the motor 14 rotates the magnetic disk 16, as indicated by the arrow R, an air bearing is formed under the read/write head 24 causing the read/write head to lift slightly off of the surface of the magnetic disk 16, or, as it is commonly termed in the art, to “fly” above the magnetic disk 16. Data bits can be written or read along a magnetic “track” of the magnetic disk 16 as the magnetic disk 16 rotates past the read/write head 24. The actuator 18 moves the read/write head 24 from one magnetic track to another by pivoting the arm 20 and the suspension 22 in an arc indicated by arrows P. The design of magnetic disk data storage system 10 is well known to those skilled in the art.
The magnetic disk data storage industry has been very successful at deriving ever greater data densities on magnetic disks 16 by pursuing the miniaturization of various components such as the read/write head 24. In particular, the miniaturization of the read/write head 24, in combination with advances in their designs and the surfaces of magnetic disks 16, has enabled ever increasing data densities by allowing the read/write head 24 to fly ever closer to the surface of the magnetic disk 16. Lower fly heights are advantageous because the decreased spacing between the read/write head 24 and the magnetic disk 16 allows for smaller data bits to be written to the magnetic disk 16 and for smaller data bits to be sensed by the read element of the read/write head 24. Unfortunately, lower fly heights also increase the likelihood that the flying read/write head 24 will collide catastrophically (“crash”) with the magnetic disk 16. Thus, establishing a fly height for a particular magnetic disk data system 10 encompasses a trade-off between higher data density and the probability of a crash.
As is well known in the art, once an optimum fly height for a particular magnetic disk data system 10 is chosen, an air bearing surface (ABS) for the read/write head 24 must be designed. The ABS should be designed to allow the read/write head 24 to maintain the desired fly height over a range of operating conditions including the changes in air flow speed and direction as the read/write head 24 is moved between tracks on the magnetic disk 16. An additional operating condition that should be taken into account when designing an ABS is the changes in ambient air pressure that the magnetic disk data system 10 will experience when operated at varying elevations. The desire to be able to manufacture one read/write head 24 that will be compatible with different magnetic disk data systems 10 has lead to another ABS design goal, namely the ability to maintain the desired fly height over a range of different magnetic disk 16 rotation rates. A further consideration in ABS design is simplicity in fabrication which can be realized by limiting the number of processing steps. Accordingly, what is desired is an ABS design that can provide a read/write head with a fly height that has greater insensitivity to changes in both magnetic disk rotation rate and ambient air pressure, and that may be fabricated without additional processing steps.